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Inventory no. 77457 - Former Display Label

Italian MECHANICAL EQUINOCTIAL DIAL
Early 18th century.

Brass; on wooden base. Signed, "Dominicus Lusuerg Mutinensis (i.e. of Modena) Faciebat Rome."; undated.

The base-plate of the instrument is fixed, at its centre, into a wooden base (the upper part of which can revolve) and can be levelled by means of four screws. Originally there were two plumb levels fixed to the base-plate. On the base-plate is a scale marked, "Arcus pro loci declinatione inuenienda"; over this scale moves a pointer attached to the rest of the instrument.

The hinged equatorial dial-plate may be set to any lattitude by adjusting the upright plates beneath it.

Over the main equatorial dial-plate, which is graduated in ordinary hours and in degrees, are two other plates showing respectively Italian and Babylonian hours. These may be correctly adjusted in relation to the ordinary hour-scale by means of two index arms which move over latitude and date scales marked under the main equatorial plate.

Over the hour-scales on the equatorial-plate moves an index-arm attached to a moveable disc on which are fixed the sights. The sights are adjustable for the declination of the Sun at any date in the year.

When the instrument is correctly adjusted, and the sights turned towards the Sun, the time is given in ordinary, Italian and Babylonian hours.

[I.120]
Lewis Evans Collection.

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